The present invention is directed to gaming machines and more particularly to optical displays provided on spinning reels of slot machines.
Conventional slot machines employ spinning reels having multiple symbols on each reel. When a player initiates a play on a slot machine, each of the reels of the slot machine begins spinning. At some point, due to friction or electronic control, for example, the reels will come to rest with one or more symbols per reel displayed through a display window. Certain combinations of displayed symbols are designated as winning combinations. When a play concludes with a winning combination being displayed, a payout may be awarded to a player.
In traditional mechanical slot machines, each reel of a slot machine might have, for example, twenty-two stops or symbols which can be displayed as part of a multiple reel payline combination. The odds of any particular combination appearing is given by the product of the number of symbols on the first reel times the number of symbols on the second reel times a number of symbols on a third reel, etc. If there are twenty-two symbols on each reel of a three-reel slot machine, the odds of obtaining any given combination are twenty-two times twenty-two times twenty-two or one in ten thousand six hundred forty eight plays. Thus, the maximum jackpot payable by such slot machine is limited to the amount that could be paid one in every ten thousand six hundred forty eight plays (i.e., about $2,600 for a quarter slot machine).
While the payout opportunity afforded by conventional slot machines may be sufficiently exciting to many players, other players desire the opportunity to win a much larger jackpot. To make this possible, additional reels could be provided or additional symbols per reel could be provided. Unfortunately, neither of these solutions is acceptable. It has been observed that slot machines having four or more reels are less appealing to players. In addition, it is difficult to provide more than about 25 symbols per reel because the reel then becomes too large to fit within the physical dimensions of the standard-sized slot machine.
An alternative technique for increasing the jackpot size in slot games employs a "virtual reel." This technique is described in U.S. Pat. No. 4,448,419 (issued to Inge S. Telnaes and assigned to International Game Technology), which is incorporated herein by reference for all purposes. The virtual reel is actually a software program which randomly selects one symbol from a very large collection of possible symbols. For example, there may be one hundred twenty-eight different stops available on the virtual reel. That is, there may be a one in one hundred twenty-eight chance of obtaining a particular symbol on the virtual reel. During a play, a symbol is randomly selected from the virtual reel. At the same time, a physical reel is spinning and observable by a player through a display glass. The outcome of the software's random selection of a symbol is then assigned to one of a smaller number of stops on the physical reel. A control circuit then causes the spinning reel to stop at the symbol selected by the software. The software controls the outcome of the game and the physical reel merely acts as a display device, making higher odds possible and offering a much larger jackpot.
If there are only twenty-two stops on the physical reel and one hundred twenty-eight stops on the virtual reel, then multiple stops on the virtual reel must be assigned or correspond to a single stop on the physical reel. To reduce the odds of some symbol combinations, certain stops on the physical reel must be represented by fewer virtual positions than others on the virtual reel.
Most casino slot games produced today, including progressive games, employ virtual reels as described above. While such games have met some needs of the industry, alternative techniques for generating larger jackpots for slot games would be desirable.